A climatic reconstruction in historical times based on the freezing date records and sediment cores at Lake Suwa

点击翻译按钮获取中文摘要

In the summer of 1996, we extracted 2m long (around 800 years) sediment core samples from Lake Suwa using a piston corer. Sampled lake sediments were sliced in every 2.5 cm to analyze the color quality, the magnetized ratio, the specific gravity, the mineral composition, and the content of carbon, nitrogen and sulfur. The results show that organic carbon content is an effective indicator of climatic variations. Thus we examine the relationship between the organic carbon content of Lake sediment cores and the freezing dates of Lake Suwa for the last 500 years.An attempt was made to estimate winter temperatures based on the long term record of the freezing dates of Lake Suwa using the linear regression equation (r=0.80). Estimated winter temperature time-series indicated that early 1600's was a coldest period, whereas both 1480's and 1540's were relatively warm. Temperature showed increasing trend from 1750's to 1860's, during which severe famine occurred frequently in Japan.